video fire & science #1

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. . . more than fighting fires

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Fire Behavior & Extinguishment Theory


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Video

Fire & Science#1


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Objectives (1 of 3)

Discuss the type of heat measurement.Discuss the fire tetrahedron.Identify the physical states of matter in which fuels are found.Describe the methods of heat transfer.Define flash point, flame point, and ignition temperature as they relate to liquid fuel fires.

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Objectives (2 of 3)

Define the relationship of vapor density and flammability limits to gas fuel fires.Define Class A, B, C, D, and K fires.Describe the phases of fire.Describe the characteristics of an interior structure fire.


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Objectives (3 of 3)

Describe rollover and flashover.Describe backdrafts.Describe the principles of thermal layering within a structure.


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IntroductionUnderstanding of fire behavior is the basis for all firefighting principles and actions.Understanding fire behavior requires knowledge of physical and chemical processes of fire.

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Types of Heat MeasurementSpecific heat is the amount of heat a substance absorbs as its temperature increases

Latent heat is absorbed as a substance is converted from a solid to a liquid or from a liquid to a gas

CSFM


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4 Types of Heat MeasurementCelsiusKelvinFahrenheitRankine

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TypesA Celsius (centigrade) degree (°C) is 1/100th

the difference between the temperature of ice melting & water boiling at 1 atmosphere pressure

0°C=melting point100°C=boiling point

A Kelvin degree (°K) is the same measurement as the Celsius degree

Zero on the Kelvin scale is –459.67°FAbsolute lowest achievable temperatureUsed by scientistCSFM

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TypesA Fahrenheit degree (°F) is 1/180th the difference between the temperature of melting ice & boiling water (1atmosphere pressure)32°F = melting point212°F = boiling point

A Rankine degree (°R) is the same size as the Fahrenheit degreeZero is -459.67°F

Also provides an absolute temperature

CSFM


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Heat UnitsJoule

Energy at work; (1 Newton) moves a body (1 inch)Watt

Measure the rate of energy releaseWatt = 1 Joule per second;

CalorieAmount of heat required to raise 1 gram of water 1°C

British Thermal Unit (BTU)Amount of hear to raise 1 pd of water 1°FCSFM


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Temperature MeasurementExpansion of a solid, liquid or gasChange of state

Solid to liquidEnergy change

Changes in electrical potential energy (Voltage)

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ThermometersLiquid expansion

Consists of a tube (partially filled with a liquid) which measures the expansion and contraction of the liquid with changes in temperature.

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ThermometersBimetallic

Contains strips of 2 metals (laminated) with different coefficients of expansion

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ThermocoupleThis thermocouple wire is used to measure the difference in temperature between its two junctions. Its great range makes it ideal for studying flame temperatures.A temperature

difference will cause a voltage to be developed that is temperature dependent.CSFM

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PyrometerMeasures the intensity of radiation from a hot object.

CSFM


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Types of Heat MeasurementEssentially, ignition is a matter of increasing temperature by adding heat, whereas physical fire extinguishment usually is accomplished through reduction of temperatures by removing the heat. By understanding temperature and the measurement of heat, you will be better able to combat fire with the proper heat removing substance. The four types of temperature units are Celsius, Kelvin, Fahrenheit, and Rankine.CSFM


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FuelWhat is actually being burnedPhysical states

SolidLiquidGas

Combustion occurs when fuel is in a gaseous state.

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Fuel


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Video

Only Gases Burn#2


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Heat EnergyMeasurement of molecular movement in a substanceWhen heat comes in contact with a fuel, the energy supports the combustion reaction.States of matter

SolidLiquidGaseousCSFM

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SolidsMost fuels are solids.Pyrolysis releases molecules into atmosphere.

Converts solid to a gas

Solids with high surface to mass ratio combust more easily and rapidly.


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SolidsSolids

Definite size and shapeSurface area in relation to massIncrease in surface area to mass, decreases the amount of heat required to cause ignition.CSFM


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Assume the shape of their containersSpecific gravity

Water has a specific gravity of oneSolubility in waterLiquids with a high surface to volume ratio vaporize and combust more easily and rapidly.

Liquids

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Vaporization The release of a liquid’s molecules into the atmosphere.An increase in surface area to volume, increases the rate of vaporization.

Liquids


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Vaporization


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Have neither shape nor volumeAssumes the shape of their containerExpand indefinitelyFuel to air mixture must be within a certain range to combust.Vapor density

Air has a vapor density of one

Gases

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Sources of Heat Energy

ChemicalElectricalMechanicalNuclear

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ChemicalHeat of combustionSpontaneous heating

Oily rags (linseed)Heat of decomposition

Hay barnsMulch piles

Heat of solution

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Chemical

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ElectricalResistance heatingDielectric heatingInduction heatingLeakage current heatingHeat from arcingStatic electricity heatingLightening

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Electrical

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MechanicalHeat of frictionHeat of compression

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Nuclear Heat EnergyRelease of large quantities of energy from the nucleus of the atom

FissionSplitting of atoms

FusionCombining of two atomsCSFM


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Sources of Heat EnergyThe process of combustion follows the basic laws of the natural sciences. Heat is a form of energy. It is a measurement of molecular motion in a substance. There are four common sources of heat energy: chemical, electrical, mechanical, and nuclear.

CSFM


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Oxygen and Oxidizing AgentsOxygen is required to initiate and sustain combustion.Normal is 21%

Minimum to allow free burning is 16%Materials classified as oxidizers will support the combustion of other materials, even if no oxygen is present.Oxidizing agents are Bromates & Chlorates

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Oxygen


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HeatRequired to ignite a fire, it is the energy componentIt causes pyrolysis or vaporization of solids & liquids & produces ignitable vaporsProvides the energy necessary for ignitionCauses the continuous production of ignitable vapors

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HeatEnergy to produce an ignition comes from a variety of sources:

Mechanical energyChemical energyElectrical energy

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Chemical Chain ReactionFlaming combustion occurs when heat energy produces continuous fuel vapors

Called a chain reactionEach reaction adds to the next

Example: Runaway nuclear chain reaction

Chain reactions continue to occur as long as there is sufficient fuel, oxygen, and heat.Interrupting the chain reaction puts the fire out.

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Chemical Chain Reaction

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Fire Triangle and TetrahedronThree basic factors required for combustion:

FuelOxygen (oxidizing agent)Heat

Chemical chain reactions keep the fire burning.

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Fire Tetrahedron


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Combustion Process ElementsCombustion occurs only during the presence of certain elements. It must be understood that the removal of any one of the elements will result in the extinguishment of the fire. These components are described as the fire tetrahedron. Each component must be in place for combustion to occur.

CSFM


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Products of CombustionThe specific products depend on:

FuelTemperatureAmount of oxygen available

Few fires consume all available fuel.

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Products of CombustionWhen a fuel burns there are four products of combustion

Fire gasesFlameHeatSmoke

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Fire GasesDetermined by the type of material, amount of available oxygen, rate of heating & temperature.Refer to as the vaporized products of combustionParticles contain carbon

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Fire GasesThe most common fire gases are:

Carbon monoxideCarbon dioxide

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Other GasesNumerous gases are released during all phases of combustion

Sulfur dioxidePhosgene Nitrogen oxidesHeroleinAmmoniaHydrogen cyanideHydrogen sulfateHydrogen chlorideAsphyxiant gasesIrritant particlesCSFM


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Asphyxiant GasesThose products of combustion that effect the central nervous system and can result in loss of consciousness or death due to oxygen depletion

Carbon monoxideHydrogen cyanideCarbon dioxide

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Irritant GasesAffect

BreathingEyesSkin

ExamplesHalogen acidsNitrogen oxidesOrganic irritantsCSFM

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FlameFlame is the luminous aspect of burningHotter flame

Less luminousMore complete combustion

Not present during smoldering phase

CSFM


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HeatA form of energy that is measured in degrees of temperature to signify intensityHeat is the combustion product most responsible for fire spread in a buildingDirect cause of burn injuriesOther injuries are:

Dehydration, heat exhaustion, respiratory tractCSFM


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SmokeAirborne products of combustionConsists of:

ParticlesVaporsGases

Inhalation of smoke can cause severe injuries.CSFM

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SmokeIt is a mixture of oxygen, nitrogen, carbon dioxide, carbon monoxide, and mixture of finely divided carbon particles (soot)Contents of smoke varies with fuel being burned. Can be hot and/or toxic.

Liquid fuels give off dense, black smoke.

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SmokeSmoke vapors

Small droplets of liquids suspended in airCan be oils from the fuel or water from suppression efforts

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SmokeWhen a material burns, it gives off products of combustion. These are gases, flame, heat, and smoke. Alone or in combination, they can cause serious injury or death to the unprotected fire fighter. Many gases are asphyxiates or irritants. It is, therefore, important that we recognize the dangers inherent in the fire environment and use the appropriate personal protective equipment and equipment in order to operate safely.CSFM

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Smokes Physical PropertiesRelative Toxicity

Ability of substance to do harm within the body measured in parts per million (ppm)Permissible exposure limits (PEL) determined by ppmExample

Carbon monoxide• PEL 35ppmCSFM


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Water solubilityA liquid’s ability to mix with waterWater soluble liquids

AlcoholCorrosivesPolar solvents

NonsolubleNonpolar solventsPetroleum products


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Vapor Density

Weight of a gas in relation to air

Air = 1

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Vapor Density Gases lighter than airHeliumAmmoniaHydrogenAcetyleneMethaneIlluminating gasesNitrogenCarbon monoxideEthylene


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Vapor DensityGases heavier than air

Gasoline vaporPropane


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Video

Vapor & Fire#3

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FlammabilityRelates to flammable limits or flammable range

Flammable explosive limitThe concentration level of a substance at which it will burn

Flammable range (FR)Ratio of gas to air that will sustain combustion if exposed to an ignition source


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Warning PropertiesMost products of combustion have an adverse affect on the bodyBurning skinBurning eyes

Increase respirationsAltered level of consciousnessAcrid smellsDizzinessNauseaVomiting


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Physical Properties of CombustionIt is crucial for the fire fighter to understand and recognize the common combustion gases and their adverse effects. Many toxic by-products of combustion do not have any warning signs. A fire fighter can be exposed to high levels of carbon monoxide and not be aware until it is too late. The fire fighter must also understand that not all gases and liquids weigh the same. This knowledge plays an integral part of fire fighter safety and the decision-making process.

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Heat TransferCombustion gives off heat which can ignite other nearby fuels.Heat energy always flows from hotter to colder. Object will achieve the same temperature if the remain in contact.Three methods of heat transfer

Conduction ConvectionRadiation


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ConductionHeat transferred from one molecule to another (direct contact)Conductors transfer heat well.

Example: Nails, Steel beams, Metal pipe

Insulators do not transfer heat well.

Example: Fiberglass


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Conduction

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ConvectionMovement of heat through a fluid medium such as air or a liquidHeated air rises, cool air sinksPrimary cause of vertical and horizontal spreadCreates convection currents


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Convection


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Convection within a RoomHot gases rise, then travel horizontally.Gases then bank down a wall or move outside the room.

HorizontallyVertically

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RadiationTransfer of heat in the form of an invisible electromagnetic waveHeat radiated to a nearby structure can ignite it.Radiated heat passing through a window can ignite an object.


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Radiation


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Heat TransferHeat is transferred in three and only three ways. It may be conducted through a substance, convected by a substance, or radiated from one substance to another. An example of conduction is a spoon in a hot bowl of soup. The handle becomes hot by the heat being conducted up the spoon.

CSFM

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Liquid Fuel Fires (1 of 3)

A liquid must vaporize before it burns.A minimum and maximum concentration of vapors must be present to ignite.Most flammable liquids can ignite well below their boiling point.


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Conditions required for ignition:

Fuel-air mixture within flammable limitsAn ignition source with sufficient energySustained contact between ignition source and fuel-air mixture


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Flash pointLowest temperature at which vapor is produced

Flame point (or fire point)Lowest temperature at which sufficient vapors are produced to support a small flame for a short time

Ignition temperatureTemperature at which the fuel-air mixture will spontaneously ignite

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Gas Fuel Fires (1 of 2)

Vapor DensityWeight of a gas fuelGas with vapor density less than 1.0 will rise.Gas with vapor density greater than 1.0 will settle.Knowing vapor density helps predict where the danger of ignition will be.


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Gas Fuel Fires (2 of 2)

Fuel-air mixtures only burn when mixed in certain concentrations.Flammability/explosive limits

Below the lower flammability limitToo little fuel = too lean

Above the upper flammability limitToo much fuel = too rich


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Explosion

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ExplosionA rapid release of high-pressure gas into the environmentThe high-pressure release, dissipating in the form of a shock wave


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Types & Causes of ExplosionsPhysical

Most common typeExternally heated container

BoilerPressurized gas cylinderTrapped steamAny container that will pressurize with the application of heat


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BLEVE (1 of 3)

Boiling Liquid, Expanding Vapor ExplosionOccurs when a tank storing liquid fuel under pressure is heated excessively

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BLEVE (2 of 3)Sequence:

Tank is heatedInternal pressure rises beyond ability to ventTank fails catastrophicallyLiquid fuel at or above boiling point is releasedLiquid immediately turns into a rapidly expanding cloud of vaporVapor ignites into a huge fireball


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BLEVE (3 of 3)

BLEVEs can injure and even kill fire fighters and civilians.

Fireball created by the ignition of expanding vaporsLarge pieces of the tank propelled great distances


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Video

BLEVE#4

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Physical/chemicalExternal heat required to cause endothermic reaction

Endothermic=absorbs heatChemical that absorbs external heat to create a chemical reactionChemical reaction creates additional heat which increases gas pressure


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ChemicalExothermic

Produces own temperature increaseDoes not require external heat to react

The higher the temperature, the faster the reaction, the more gas is produced


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Chemistry of Combustion (1 of 2)

Exothermic reactionsReactions that result in the release of heat energy

Endothermic reactionsReactions that absorb heat or require heat to be added

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Chemistry of Combustion (2 of 2)

OxidationChemically combining oxygen with another substance to create a new compound

CombustionRapid, self-sustaining process that combines oxygen with another substance and results in the release of heat and light

PyrolysisDecomposition of a material caused by external heating


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Classes of Fire (1 of 2)

Fires classified according to type of fuelExtinguishing agents classified to match type(s) of fires they extinguishA fire can fit into more than one class.


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Classes of Fire (2 of 2)

Five classes of fires:Class AClass BClass CClass DClass K

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Class AFuel: Ordinary solid combustibles

WoodPaperCloth

Extinguishing agents:Water (cools the fuel)


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Class BFuel: Flammable or combustible liquids

GasolineKeroseneOils

Extinguishing agents:Foam or carbon dioxide Dry chemicals


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Class CFuel: Energized electrical equipment

Underlying fuel is often Class A or Class BSpecial classification required due to electrical hazards

Extinguishing agents:Carbon dioxideUse of water is not advised.

Be sure to shut off power before using water.

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Class DFuel: Burning metals

PotassiumLithiumMagnesium

Extinguishing agents:Special salt-based powders or dry sandDo NOT use water.


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Class KFuel: Combustible cooking media

Cooking oilsGrease

Extinguishing agents:Designation is new and coincides with a new classification of Class K extinguishing agents


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Methods of ExtinguishmentCool the burning material.Exclude oxygen.Remove fuel.Break the chemical reaction.

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Methods of Extinguishment


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Extinguishing AgentsWater

Extinguishment principlesCooling a solid or liquidCooling the flame itselfDiluting oxygen


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Water UseClass A firesClass B fires

Certain instancesClass D fires

Very limited

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Water Physical PropertiesFreezes at 32°F or 0°CBoils at 212°F or 100°CWeighs 8.34 pounds per gallonNon-compressibleHigh surface tensionTakes shape of containerNeeds expellant force in most casesExpands 1700:1, steam


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Advantages of WaterAbsorbs large amounts of heatPlentifulCan be used with specialized agents


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Disadvantages of WaterConductor of electricityHigh surface tensionFreezesReacts with certain chemicalsWeight

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Carbon Dioxide (CO2)Extinguishment principles

Oxygen reductionSmothering effect

Limited cooling effects


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CO2 UseClass A fires

Limited instancesClass B firesClass C fires


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CO2 Physical PropertiesNormally a gasLiquefied under temperature & pressure1 ½ times heavier than airSolid below - 79°F

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CO2

AdvantagesHigh expansion ration

1 pd liquid = 8 cf of gas

Readily turns from liquid to gasProvides its own pressureNonconductor

DisadvantagesSlightly toxicWater solubleLimited effect on Class A combustibles


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Halogenated Hydrocarbons(Halons)


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HalonsExtinguishment principles

Break the chain reactionSome cooling

Halos can be use onClass A fires

Special instancesClass B firesClass C fires

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Phases of FireFour distinct phases:

IgnitionGrowthFully DevelopedDecay


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Ignition PhaseFirst phase of fire development3 elements of fire are present

FuelHeatOxygen

Fuel is heated to its ignition temperature starting the chemical chain reaction.


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Ignition Phase

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Growth PhaseSecond phase of fire developmentAdditional fuel involvedFire grows largerConvection draws more air into fireThermal layering:

Hot gases collect at ceiling and bank downward.


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Growth PhaseIncreasing heat begins to generate

Mushrooming & rollover occurProducts of combustion reach the outer walls of the compartmentProducts of combustion bank from the ceiling down


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Growth Phase

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Growth PhaseIncreasing heat begins to generate

Thermal layering:Gases form in layers according to temperatureHottest gases on top, cooler on bottomThe heat from rollover radiates back down and heats uninvolved fuel sources liberating flammable gases contributing to flashover & firefighter injuries


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Growth PhaseSmoke temperature can be up to 900°FRoom heat will increase proportionately to the time the fire burnsFire gases being generated

Water vapor (H20)Carbon dioxide (CO2)Sulfur dioxide (SO2)Carbon monoxide (CO)


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Growth Phase

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FlashoverThe third phase of fire developmentTransition point between growth phase and fully developed phaseAll combustible materials in a room ignite at once.Temperatures range from 900°F – 1,200°F.Flashovers are deadly!


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FlashoverSuper-heated fire gases have heated nearby unburned combustibles liberating flammable fire gasesWhen the temperature reaches the ignition point of another substance in the room, a new chain reaction combustion site occurs and additional heat is added beyond the initial source of the fireFlashover is not instantaneous but occurs rapidly


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Flashover

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Fully Developed Phase

Fourth phase of fire development.All combustible materials in the room are burning.


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Heat produced at maximum rateOxygen consumed rapidlyFire will burn as long as fuel and oxygen remain.This fire is ventilation controlled.


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Decay PhaseFirth phase of fire developmentFuel/oxygen or both is nearly exhaustedIntensity reducesEventually fire will go out


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Decay PhaseThe fire is now controlled by

FuelSufficient oxygen with low amount of fuel

VentilationCompartment is not ventedThere is plenty of fuel heated to its ignition temperature

• Backdraft


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Video

Phases of Fire#5

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Phases of FireFire development is defined in five phases: ignition, growth, flashover, fully developed, and decay. Each phase presents dangers that can cause serious injury or death to fire fighters and occupants. As a fire transitions through each phase, its dangers lead to the next. During the flashover phase, fire develops so rapidly that it is a very short time for the fire to enter the fully developed phase. It is crucial for the fire fighter to identify and recognize the different phases to employ proper fire attack tactics.


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Interior Structure Fire CharacteristicsFire is fully or partially contained within a buildingBuilding acts as a box.Special considerations:

Room contentsFuel load and fire spreadFlashover, rollover, backdraft, and thermal layering


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Room ContentsMany fires burn only the contents, and not the structure itself.Modern rooms contain many plastic and synthetic materials.Furniture may have little resistance to ignition from flaming sources.Wall and ceiling finishes can burn readily.

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Fuel Load and Fire SpreadTotal quantity of combustibles in a roomDetermines how much heat and smoke will be generatedSize, shape, and arrangement of fuel will affect combustibility and fire spread


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Special ConsiderationsFour conditions particular to interior fires that affect fire fighter (and civilian) safety:

FlashoverFlameover (or rollover)BackdraftThermal layering and thermal balance

However, before we discuss these in detail we must discuss Pyrolysis.


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PyrolysisChemical decomposition of matter through the action of heatAlso known as

Pyrophoric actionPyrolysisPyrophoric carbonization

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Pyrolysis ProcessAs a fuel is heated the surface reaches the boiling point of water, & water vapor is releasedAs heating continues/increases, the drying process continuesEarly indications of the pyrolysis process in addition to steam is the darkening or discoloration of the surface of the fuel


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Pyrolysis Process


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Pyrolysis Process continued

As pyrolysis continues combustible gases are released and a black carbon residue remainsAs pyrolysis continues sufficient combustible gases are evolved to produce an atmosphere rich enough to support combustion.

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Thermal Layering & BalanceSuperheated gases collect near ceiling.Temperatures are lowest near floor.Fire streams create steam which expands and rises.


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Thermal Layering & BalancePrevention:

Coordinate fire attack with ventilation.Use straight streams to minimize steam formation.


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Rollover (Flameover)When in a compartment, heated products of combustion are producedThe seat of the fire continues to heat these fire gases to their ignition temperature where they spread across the ceiling levelHeat from rollover radiates back down & further heats nonburning materialThis radiant heat is a major contributor to flashover

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Rollover


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Rollover (Flameover)A warning sign of imminent flashoverLicks of flame ignite briefly in upper layers of smokeSituation calls for aggressive cooling of atmosphere, immediate exit, or immediate ventilation


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Dangers of RolloverReduces chance of survivabilitySlows interior fire attack to the seat of the fireIncreases for potential of vertical fire extension

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Prevention of RolloverApply short bursts of water to the upper levels of the thermal layerVertical ventilation

Removes super-heated gases that contribute to the ignition temperature of combustibles


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Rollover Thermal LayeringForms layers of heated gases according to temperature

Hottest gases in the top layer, cooler in the bottom

Also know as heat stratification or thermal balanceImproper water application may disrupt the thermal layering, bring super-heated gases down to the firefighter


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Rollover

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Rollover Thermal Layering


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FlashoverA transitional phase between the growth stage & fully developed stage of a fireExtension of open flames from the original room out through the openingsOpen-flame combustion of all combustible materials in a compartment


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Signs of FlashoverYou are not near the seat of the fire, but there is excessive heat in the smokeThick, hot smoke under pressureRollover & fingers of fire developing in the thermal layer

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Prevention of FlashoverEarly recognitionProper ventilation

VerticalHorizontal

Proper use of hose streams to cool super-heated gases

Do not disrupt the thermal balanceStraight or solid streams to limit steam production

Extinguish the seat of the fire


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Backdraft (1 of 5)

Explosion that occurs when oxygen is suddenly admitted to a confined area that is very hot and filled with combustible vapors


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Backdraft (2 of 5)

Usually occurs when a fire is smoldering (decay phase)

Room is filled with carbon monoxide and other products of combustion.The oxygen is consumed before the fuel is consumedSudden introduction of air will explosively feed the fire.

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Backdraft (3 of 5)

Signs of an impending backdraft:Little or no flame visibleSmoke emanating under pressure from cracksNo large openings“Living fire” visibleUnexplained change in color of smokeGlass (windows) smoke stained or blackenedSigns of extreme heat


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Backdraft (4 of 5)

Signs of an impending backdraft:Tightly sealed buildingSmoke pushing out the top of a window at high pressure and being sucked back in from the bottom of the window


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Backdraft

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Backdraft (5 of 5)

Prevention of backdrafts:Ventilate at a high level to allow superheated gases to escape

It is crucial that the vertical opening be made prior to the horizontal opening

• Well-coordinated fire attack


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Backdraft


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Video

Backdraft#6

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Backdraft & FlashoverBackdraft and flashover are two very significant fire conditions that can lead to fire fighter injury and deaths. It is crucial that fire fighters recognize the difference between flashover and backdraft. Although the devastating results are very similar, backdraft and flashover are very different.


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Backdraft & FlashoverFlashover is the transitional phase of fire between the growth of a fire and it being fully developed. Flashover is associated with heavy fire and super-heated combustibles that reach their ignition temperature.


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Backdraft & FlashoverBackdraft is associated with relatively no fire and all products of combustion and unburned fuels are already at their ignition temperature. Backdraft is a ticking time bomb awaiting an unsuspecting fire fighter to add a breath of fresh air.

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Summary (1 of 3)

To be a successful fire fighter you must know fire behavior.Characteristics of solids, liquids, and gases are different.Fire triangle and fire tetrahedron represent conditions necessary for combustion.


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Summary (2 of 3)

Five classes of fire require specific extinguishing methods.Knowledge of heat transfer is required to understand how fires propagate.Typical fires pass through four distinct phases.


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Summary (3 of 3)

Liquid fuel fires, gas fuel fires, and interior fires have unique characteristics.Flashover, rollover, backdraft, and thermal layering are conditions that threaten fire fighters and victims.

video fire & science #1

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